Ducman82

Driving this evening I noticed a knocking sound when parked in nutral but only when i rev the engine then take my foot off the gas...... Sounds like it from the clutch area, but I've never had a clutch issue, shifts fine.... Hummmm

Ducman82

http://i575.photobucket.com/albums/ss197/Ducman82/78b836fe.mp4

Here is a link To a video I took. Oil pressure is great.

NC928S4

Could it be something vibrating/ rubbing on the forward heat shield? Or possibly a loose bolt-washer vibrating. Lastly and unfortunately, it sounds more like a noisy bearing.

Ducman82

When I get home im going to get this puppy in the air. Maybe some kind of exhaust bracket/ heat shield rattle.... But would a rod make that noise on decel only? I'd figure a rod would do it all the time, even idle....

Fabio421

That sounds like somethings loose under there. It doesn't sound like a knock to me. Crawl under there and find it so you can set your mind at ease.

cpayne

maybe a loose hanger

Ducman82

I'm sitting in my math class going crazy with horror possibilities going around in my head . Almost out of class then, ten. 5 mile drive home. The. Up in the air it goes

namasgt

Did you change the bushing under the air box for the clutch arm?

Ducman82

Well.......... got her up in the air on lift bars and had the wife start it and give her a little gas.... sound is definitely from the engine. i used my stethoscope and and touched it to the clutch bottom cover got no noise, but i DID get the noise from the headers... more so from the driver side rear. could a pilot bearing do that? I'm thinking a Rod (worst case) but oil pressure seems good.

i think the 4.5 knows I'm building another motor....... so its mad...

Mrmerlin

pull the dipstick and drip the oil onto black cardboard look at the oil in the sun with a magnifying glass if you see metallic s then your gonna have to go deeper

Ducman82

i checked the oil and it looked ok. but ill do the sun trick tomorrow.

snoz

I'm not familiar with a 928 rod knock noise, but this doesn't sound like any rod or main knock I've ever heard on other motors.

Ducman82

that what i thought too. its not 100% constant. but varies in pitch with the throttle/RPM's.
im swinging it by the 928 shop here in town and my buds going to check it out and verify. i hope its stupid simple, but from what i could/couldnot find under the car....... ill plan for the worst.

namasgt

If that sound was from the engine internal, it would have blown up by now. That doesn't sound like a rod knock. Go back under the car and take the rubber plug off of the bottom of the bell housing, where you can see the slave cylinders rod. have someone rev the engine while you're looking and see if the rod moves side to side.
You are saying no sound from the bell housing but its hard to tell with everything bolted up together. I had someone complain about their 84 5 speed making the exact same rattling sound every time the engine was revved. The Release lever had come loose banging against the bell housing. It could be something else, like a loose exhaust bolt. But I would check the release arm first. Did you change the bushing for the release arm?

Ducman82

i have yet to replace that bushing, but i did not se any side to side movement from the slave when i was down there. looked up with a light too... but being that everything is spinning quite fast, did not see much. could a throwout do it?